Tool holders in manufacturing machines have a tendency to vibrate and give rise to noise when in use. Such vibration disturbs the work process by having a negative effect on the accuracy of the result. The vibrations also give rise to a troublesome disturbing noise that worsens the environment around the manufacturing machine.
A perfect manufacturing machine does not give rise to any vibrations, and all energy is passed to the process that is to be carried out. In practice, vibrations always arise when the various parts of the machine work against each other. As the machine becomes more and more worn, changes in its dynamic properties take place. This means that new types of vibration can arise during different periods of the lifetime of the machine. The vibrations can lead to poor surface finish of the work piece, further wear on the machine and on tools, with, in the worst case, irreparable damage as a consequence.
During the processing of metal materials, problems also arise that are caused by the high level of noise caused by vibrations from the processing and the noise of the machine. Tools that have been used up until the present have not had built-in or subsequently added damping arrangements of such a type that sufficient damping of sound and vibration has been possible. It is important to be able to remove major parts of the vibration noise within the frequency interval that is uncomfortable for the human ear. It is desirable that the level is reduced to a level under 80 dB.
The arrangement of a vibration-damping material in a longitudinal track on a tool holder is previously known through U.S. Pat. No. 2,426,359. The aim is to completely damp the vibrations, or at least to reduce them significantly.
A tool holder is previously known through WO 02/45892 A1 (FIG. 14) with a damping element. The distance between the damping element and the tool body is such that a relative motion between the tool body and the damping element is permitted during processing.
A tool holder for several tools is previously known through U.S. Pat. No. 5,033,340 A. An aperture is present in the connecting surface between each tool and the tool holder, and a “damping sandwich” construction is arranged in this aperture. This design consists of alternating layers of steel and viscoelastic material. It is considered that this design reduces noise.
Previous attempts to solve the problem of vibrations have thus contained complicated solutions with weights and fluids in cavities in the tool holder intended to oscillate with inverted phase relative to the undesired vibrations and in this way to cancel them out. Other solutions demonstrate material arranged on the surface of the tool holder intended in the same manner to oscillate with inverted phase for cancellation of the vibrations. These solutions in general involve troublesome dimensioning procedures and testing procedures before the correct material and properties are found, even if this is possible at all.
One aspect of the present invention is thus to achieve a tool holder with the conditions required to damp vibrations in a simpler manner.